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41.
Small tectonic slices of undeformed eclogites and ultrahigh-pressure granulites occur in three tectonic units of the Śnieżnik
Mts. (SW Poland). Ultrahigh-pressure granulite/eclogite transitions with peak metamorphic conditions between 21 and 28 kbar
at 800 to 1000 °C occur only in the Złote unit. Conventional U-Pb multigrain analyses of zircons from a mafic granulite provided
207Pb/206Pb ages between 360 to 369 Ma which are interpreted to approximate timing of original crystallisation from a melt. Diffusion
kinetics and the restricted availability of a fluid phase mainly controlled the conversion from granulite to eclogite, although
some bulk-chemical differences were also recognised. The ultrahigh-pressure granulites from the Złote unit exclusively contain
H2O-rich inclusions with variable salinities which distinguishes them from high-temperature (HT)-granulites world-wide. This is also in contrast to the fluid regime (H2O-N2-CO2) recognised in the lower-temperature eclogites (600–800 °C) from the closely associated Międzygórze and Śnieżnik units. The
variation in fluid composition between the lower-temperature eclogites and ultrahigh-pressure granulites on the one hand and
ultrahigh-pressure granulites and HT-granulites on the other hand probably indicates contrasting P-T-t paths as a result of different tectonic environments.
Received: 15 June 1998 / Accepted: 2 March 1999 相似文献
42.
Mobilization of Ti-Nb-Ta during subduction: Evidence from rutile-bearing dehydration segregations and veins hosted in eclogite, Tianshan, NW China 总被引:15,自引:0,他引:15
Field evidence from the western Tianshan subduction complex in northwestern China indicates that the high field strength elements Ti, Nb, and Ta were mobilized and thereby fractionated from Zr and Hf during the dehydration process that transformed blueschist into eclogite. Both a segregation with a depletion halo, thought to represent initial mobilization during dehydration, and a transport vein, indicative of the long distance transport were investigated. In each case, centimeter-sized rutile grains grew as needle-like crystals in the segregation and as prismatic crystals in the vein. Within the host rock of the segregation, the Ti contents of garnet and omphacite, the modal abundances of rutile and titanite and the bulk rock Ti, Nb, and Ta contents decrease towards the segregation. These observations are consistent with transport of Ti, Nb, and Ta from the host rock into the segregation. Textural and geochemical data for the eclogite-facies vein minerals indicate that Ti-Nb-Ta-rich fluids were transported over long-distances (at minimum meter-scale) during fracture-controlled fluid flow. Complex forming ligands (e.g., Na-Si-Al polymers and F−) may have enhanced the solubility of Ti, Nb, and Ta in the fluid. Changes in fluid composition (e.g., XCO2) may both precipitate rutile and fractionate Ti, Nb, and Ta from LILE and REE. 相似文献
43.
Reiner GOGUEL 《Geostandards and Geoanalytical Research》1983,7(2):341-344
Cadmium signals obtained by direct aspiration of highly concentrated solutions of rocks and other geochemical samples are swamped by strong matrix background signals. Mainly because of iron interference, the deuterium source or other continua are not satisfactory for background correction. In order to isolate atomic absorption by cadmium the total signal and the background signal have to be measured precisely. Sequential measurements in the double beam mode with electrodeless discharge lamps of cadmium and arsenic at 228.80 and 228.81 nm produced a set of uninterfered data for cadmium within marginally useful detection limits of (0.10 ppm in granite, 0.16 ppm Cd in limestone). Simple extraction of the sample powders with nitric acid dissolves only part of the sample matrix but most of the cadmium. In this way higher relative and absolute cadmium concentrations in solution and better detection limits are obtained (e.g. 0.02 ppm Cd in granite). This approach allows cadmium in geosamples at levels below 0.3 ppm to be determined more accurately than via hydrofluoric acid dissolution. 相似文献
44.
Reiner Klemd Siegfried Matthes Martin Okrusch 《Contributions to Mineralogy and Petrology》1991,107(3):328-342
The mineral assemblages in the eclogites and meta-sediments of the Münchberg gneiss complex suggest minimum pressures of about 15 kbar, and temperatures of 600±30° C for the eclogite-facies metamorphism. Both rock types underwent a subsequent amphibolite-facies metamorphism at almost the same temperature range. In the Weissenstein borehole the eclogites and meta-sediments show an intimate interlayering on a centimetre scale. Contacts between the two rock types are often sharp and untectonized suggesting in-situ metamorphism of the eclogites. The following features indicate that the gneisses were subjected to eclogite-facies metamorphism:
- Phengite relics and phengite inclusions in garnet contain up to 3.45 Si per formula unit while amphibolite facies phengites have considerably lower Si-contents (3.0–3.25 p.f.u.).
- Omphacite relics occur in the form of Na-augite (6–9 mol% jadeite)-oligoclase symplectites.
- Garnets with up to 40 mol% of the pyrope component occur.
45.
46.
Richard A. Feely Christopher L. Sabine Reiner Schlitzer John L. Bullister Sabine Mecking Dana Greeley 《Journal of Oceanography》2004,60(1):45-52
As a part of the JGOFS synthesis and modeling project, researchers have been working to synthesize the WOCE/JGOFS/DOE/NOAA
global CO2 survey data to better understand carbon cycling processes in the oceans. Working with international investigators we have
compiled a Pacific Ocean data set with over 35,000 unique samples analyzed for at least two carbon species, oxygen, nutrients,
chlorofluorocarbon (CFC) tracers, and hydrographic parameters. We use these data here to estimate in-situ oxygen utilization
rates (OUR) and organic carbon remineralization rates within the upper water column of the Pacific Ocean. OURs are derived
from the observed apparent oxygen utilization (AOU) and the water age estimates based on CFCs in the upper water and natural
radiocarbon in deep waters. The rates are generally highest just below the euphotic zone and decrease with depth to values
that are much lower and nearly constant in water deeper than 1200 m. OURs ranged from about 0.02–10 μmol kg−1yr−1 in the upper water masses from about 100–1000 m, and averaged = 0.10 μmol kg−1yr−1 in deep waters below 1200 m. The OUR data can be used to directly estimate organic carbon remineralization rates using the
C:O Redfield ratio given in Anderson and Sarmiento (1994). When these rates are integrated we obtain an estimate of 5.3 ±
1 Pg C yr−1 for the remineralization of organic carbon in the upper water column of the Pacific Ocean.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
48.
49.
Multiple sources for mineralizing fluids in the Charmitan gold(-tungsten) mineralization (Uzbekistan) 总被引:1,自引:0,他引:1
Torsten Graupner Samuel Niedermann Dieter Rhede Ulf Kempe Reimar Seltmann C. Terry Williams Reiner Klemd 《Mineralium Deposita》2010,45(7):667-682
Mineral assemblages present within the Charmitan gold(-tungsten) quartz-vein mineralization have been investigated for their
cathodoluminescence behaviour, chemical composition and noble gas isotope systematics. This inventory of methods allows for
the first time a systematic reconstruction of the paragenetic relationships of quartz, scheelite, sulphides and native gold
within the gold mineralization at Charmitan and provides the basis to utilise noble gas data in the discussion of sources
and evolution of ore-forming fluids. The vein quartz is classified into four generations based on microscopic and cathodoluminescence
investigations. Quartz I shows intense brittle deformation as associated scheelite I. Undeformed scheelite II overgrows scheelite
I and has lower light rare earth element and higher intermediate rare earth element contents as well as higher strontium concentrations.
Scheelite II is associated with the economic gold mineralization and formed during re-crystallisation and re-precipitation
of material which was partly re-mobilised from early scheelite I during infiltration of gold-bearing fluids. Early stage native
gold inclusions are often associated with stage 2 sulphides, scheelite II and bismuth tellurides and contain Ag (3.6–24.4 wt.%),
Hg (≤1.0 wt.%) and Bi (≤0.2 wt.%). Later stage electrum grains occur in association with stage 3 sulphides and sulphosalts
and contain Hg (<0.8 wt.%) and elevated Sb concentrations (up to 3.0 wt.%). Noble gas isotope data (3He/4He: 0.2-0.4 Ra) for hydrothermal ore fluids trapped in the gold-related sulphides and sulphosalts (stage 2 pyrite and arsenopyrite;
stage 3 pyrite, sphalerite, galena and lead sulphosalts) suggest that diverse fluid sources were involved in the formation
of the Charmitan gold deposit. These data are indicative of a small, but significant input of fluids from external, deep-seated
(mantle and possibly lower crust) sources. A decrease in the input of mantle helium and an increasing role of crustal helium
from early to later stages of the mineralization is suggested by the measured 3He/4He and 40Ar*/4He ratios. Sulphides from ore veins in meta-sedimentary rocks contain higher portions of meteoric fluids than those in intrusive
rock types as indicated by their lower 3He/36Ar ratios. The 3He/36Ar ratios in the meta-sedimentary rocks agree well with ratios typical of gold mineralizations in the Tien Shan gold province
completely hosted by meta-sedimentary sequences, indicating intense fluid-wall rock interaction. 相似文献
50.
Jeremy B. Faden Robert S. Weigel Jan Merka Reiner H. W. Friedel 《Earth Science Informatics》2010,3(1-2):41-49
Autoplot is software developed for the Virtual Observatories in Heliophysics to provide intelligent and automated plotting capabilities for many typical data products that are stored in a variety of file formats or databases. Autoplot has proven to be a flexible tool for exploring, accessing, and viewing data resources as typically found on the web, usually in the form of a directory containing data files with multiple parameters contained in each file. Data from a data source is abstracted into a common internal data model called QDataSet. Autoplot is built from individually useful components, and can be extended and reused to create specialized data handling and analysis applications and is being used in a variety of science visualization and analysis applications. Although originally developed for viewing heliophysics-related time series and spectrograms, its flexible and generic data representation model makes it potentially useful for the Earth sciences. 相似文献